What
is the ruling on someone who deliberately abandons Friday prayer
without any valid reason, and then prays Thuhr, is his prayer valid or
not?

Fatwa

All
perfect praise be to Allaah, The Lord of the Worlds. I testify that
there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It
is not permissible to abandon Friday prayer without any sound religious
reason and whoever does so, has disobeyed Allaah and subjects himself
to the severe threat mentioned in the Prophetic narration.

The Prophet said: "People
should stop missing Friday prayers otherwise Allaah will put a seal on
their hearts and thus they will be among the heedless." [Muslim]

The threat is multiplied and increased if a person misses three Friday prayers or more.

The Prophet said: "Whoever misses three Friday prayers out of negligence, Allaah will seal his heart." [Ahmad].

Furthermore, the scholars considered missing Friday prayer without any valid reason as on of the great major sins.

Ibn Al-Qayyim said: 'Among the great major sins is missing Friday prayer, as the Prophet said:

"People
should stop missing Friday prayers otherwise Allaah will put a seal on
their hearts and thus they will be among the heedless." [Muslim].'

So this is the ruling on missing Friday prayer without any valid reason.
As
regards what one should do when he misses Friday prayer, he has to pray
Thuhr prayer with the intention of Thuhr whether he missed it with a
sound reason or without a valid reason, however, he is sinful in
missing it without a sound reason. Nonetheless, his Thuhr prayer is
valid if he prays Thuhr after the Imaam has prayed the Friday prayer.
If he prays Thuhr before the Imaam prays Friday prayer then his prayer
is not accepted and he has to pray Thuhr again as Ibn Qudaamah
said.

However, he has to repent to Allaah from this disobedience and he
should not to be neglectful about Allaah's obligations on him, and he
should remember the bounties of Allaah which He bestowed on him. He
created him as a Muslim and gave him the ability to attend the Friday
prayers and endeavouring in his general benefits and affairs, so he
should not be deficient in fulfilling Allaah's obligations on him.